Separation of kainite from potassium chloride by flotation



United States Patent 3,447,681 SEPARATION OF KAINITE FROM POTASSIUM CHLORIDE BY FLOTATION Jose L. Ramirez, Agro-Quimicas de Honduras, Apartado Postal 362, Tegucigalpa, D.C., Honduras, N0 Drawing. Filed Apr. 17, 1967, Ser. No. 631,128 Int. Cl. B03d J/02 US. Cl. 209-166 8 Claims ABSTRACT OF THE DISCLOSURE A froth flotation process for separating kainite from salt mixtures containing kainite in admixture with potassium chloride, in which the collector is in the form of a compound having the formula R-C oNHX-0fi-Y -0 o OM O SOaM' where RCO-- is the acyl radical of a monocarboxylic acid containing a chain having from 12 to 22 carbon atoms, X is an alkylene or alkyl substituted alkylene radical containing from 2 to 6 carbon atoms, Y is the carbon-hydrogen residue of a 4 to 8 carbon atom di: carboxylic acid, and M and M are cations of alkali metals, or ammonium or substituted ammonium bases.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to the recovery of kainite and potassium chloride from salt mixtures containing the same. More particularly, it involves initially concentrating and separating kainite from potassium chloride and other salts in mixtures cantaining sodium chloride, epsomite and other impurities in a medium of an aqueous brine, and then recovering the potassium chloride.

Description of the prior art The concentration of kainite by flotation, and wherein the kainite is separated from potassium chloride, has heretofore been known, as disclosed, for instance, in German Patent No. 1,189,032. Flotation agents suggested for such purpose are, for example, long chain fatty amine salts, salts of higher secondary amines, and sodium oleate. Commonly, such flotation agents have been used in conjunction with supplementary frothers and dispersants to improve their performance.

It has, heretofore, been broadly disclosed that watersoluble salts of sulfodicarboxylic acid esters of higher fatty acid amides of hydroxyalkyl nontertiary amines can be used as flotation agents, as shown, for instance, in US. Patent No. 2,236,528.

SUMMARY OF THE INVENTION My invention provides a more effective, simpler, and less costly separation procedure in the selective flotation of kainite by using, in the initial step of separating the kainite from the potassium chloride and other salts in the starting raw salt mixtures, as flotation agents, watersoluble salts of sulfodicarboxylic acid esters of higher fatty acid amides of hydroxyalkyl nontertiary amines. Flotation agents are, generally speaking, highly selective in regard to types of ores and may be operative to effect flotation of certain mineral constituents from certain ores and be ineffective or worthless for the flotation of other ores. While, therefore, as pointed out above, US. Patent No. 2,236,528 has indicated, broadly, that the compounds disclosed therein have, among their uses, those for flotation of ores, no one, so far as I am aware, has suggested the possibility of their utility for the specific 3,447,681 Patented June 3, 1969 "ice where RCO is the acyl radical of a monocarboxylic, particularly fatty, acid containing a chain having from 12 to 22 carbon atoms, X is an alkylene or alkyl substituted alkylene radical containing from 2 to 6 carbon atoms, Y is the carbon-hydrogen residue of a 4 to '8 carbon atom dicarboxyclic acid, and M and M are cations of alkali metals, or ammonium or substituted ammonium bases such as lower alkyl amine radicals. I have found that such flotation agents are highly effective without the necessity for the use of any supplemental frothers or dispersants although such can be used, if desired.

DESCRIPTION OF THE PREFERRED EMBODIMENTS After the kainite has been separated from the raw ore, the potassium chloride is advantageously floated from the residue salts with a water-soluble salt of a long chain primary aliphatic amine reagent containing at least 70% by weight of amines with between 18 and 24 carbon atoms, or this separation may be achieved with flotation agents such as octadecylamine acetate or other watersoluble salts of fatty amines containing from 16 to 22 carbon atoms.

While my invention is particularly useful in separating the aforesaid salts from the decomposition of kainite and carnallite mixtures, it is also applicable to any similar salt mixture containing kainite (commonly represented as KCl-MgSO.,-2.75H O), potassium chloride, epsomite (commonly represented as MgSO '7H O) sodium chloride, and other impurities. My invention will be described below more particularly in connection with the flotation of kainite and potassium chloride from salts obtained by the decomposition of a kainite-carnallite mixture but it is understood that it is not limited thereto.

In the practice of my invention, generally speaking, a decomposed salt mixture, which typically may contain, by weight, of the order of 20% kainite, 25% potassium chloride, 5% carnallite, 20% epsomite, and 30% sodium chloride, and which includes small amounts of other impurities, is slurried as an approximately 50%, by weight, slurry with a carnallite decomposition brine, typi cally containing of the order, by weight, of 22% magnesium chloride, with lesser amounts of sodium chloride, potassium chloride and magnesium sulfate and the balance water. The slurry is conditioned with, for instance, the sodium' salt of the sulfosuccinic acid ester of the oleic acid amide of monoisopropanolamine, then diluted to about 30%, by weight, of solids with additional carnallite decomposition brine, and admitted to a flotation cell. When air is introduced to the flotation cell, a froth containing primarily kainite is formed and removed from the cell.

As mentioned above, the feed salts contain of the order of 25% potassium chloride, which remains in the residue salts of the kainite flotation. The potassium chloride is desirably recovered and, to this end, the residue salts from the kainite flatation are withdrawn from the flotation cell, and dewatered in a centrifuge or filter or other dewatering device. The residue salts are conditioned in additional fresh carnallite decomposition brine with a water soluble salt of a long chain primary aliphatic amine reagent and subjected to a second flotation. The froth formed when air is admitted to the flotation cell, said froth containing primarily potassium chloride, is removed from the cell.

The application of my invention may be further understood by the following illustrative examples. All percentages recited are by weight.

EXAMPLE 1 Raw salts from the decomposition of a kainite-carnallite mixture were slurried as a 50% slurry with a liquor from the carnallite decomposition. The compositions of the liquor and the solids, which contain about 30.8% sodium chloride, 18.5% kainite, 5.5% carnallite, 21.9% epsomite and 24.6% potassium chloride are shown in Table I.

TABLE I.ANALYSIS, PERCENT K Na Mg Cl S04 E20 Feed solid 14. 04 10. 09 4. 82 32. 35 13. 65 25. 04 Feed liquor 1. 59 0. 78 6. 56 19. 47 3. 59 68. 01

TABLE II.ANALYSIS, PERCENT Kainite float:

Na Mg 9.25 Cl 16.62 S 33.10 H O 25.38

This float contained about 95% kainite, 2.3% carnallite and 3.6% potassium chloride, and represented a yield of about 90% of the kainite in the feed salts. The residue from this flotation was filtered and conditioned with a quantity of fresh brine and an acetate of an amine mixture containing about 90% C -C straight chain aliphatic amines and about octadecyl amine, added in the portion of 100 grams per metric ton of solids. After 3 minutes of conditioning, the slurry was placed in an agitated flotation cell, and, when air was admitted, a froth containing potassium chloride formed and was removed from the cell. The analyses of the float, weighing 108 grams, and the residue are shown in Table III.

TABLE III.-ANALYSIS, PERCENT K Na Mg Cl S04 E20 KCl float 30. 74 2. 97 3. 77 34. 79 11. 75 15. 98 9. 50 10. 94-

Besidue 6.31 24.98 2.82 45.45

This second float contained about 60% potassium chloride, 30.4% epsomite, 7.6% sodium chloride and 1.9% carnallite, and represented a 76.5% yield of the potassium chloride in the feed material.

EXAMPLE 2 4 and floated in an agitated flotation cell. The froth removed from the cell was refloated, and the second froth, weighing 114 grams, was of the composition shown in Table IV.

TABLE IV.-ANALYSIS, PERCENT Kainite float:

Na, Mg K 9.31 Cl 16.31 so. 33.41 H 0 25.23

This float, containing about 97.5% kainite, and 3.3% potassium chloride, represented a yield of about 90.5% of the kainite in the feed.

The residue from this flotation was filtered and conditioned with fresh brine and the amine flotation agent used in Example 1 in the proportion of grams per metric ton of solids. Formaldehyde was added to depress the effect of the kainite flotation reagent, and the slurry was floated in an agitated flotation cell. The compositions of the potassium chloride-rich froth and the residue solids are shown in Table V.

TABLE V.ANALYSIS, PE RCENT K Na- Mg Cl S04 H O KCl float 40. 54 l. 63 1. 81 40. 76 5. 25 10. 01 Residue 5. 27 21. 70 3. 24 40. 03 10. 38 19. 38

The float, weighing 111 grams, containing about 82% potassium chloride, 13% kainite and 4.3% sodium chloride, represented a yield of 56% of the potassium chloride in the feed.

I claim:

1. A process for separating kainite from salt mixtures containing kainite and potassium chloride, which comprises subjecting said mixture, in the form of an aqueous slurry, to a froth flotation with a collector having the formula where RCO is the acyl radical of a monocarboxylic acid containing a chain having from 12 to 22 carbon atoms, X is an alkylene or alkyl substituted alkylene radical containing from 2 to 6 carbon atoms, Y is the carbonhydrogen residue of a 4 to 8 carbon atom dicarboxylic acid, and M and M are cations of alkali metals, or amm'onium or substituted ammonium bases, whereby to float off a kainite concentrate.

2. A process according to claim 1, in which the collector is a sodium salt of the sulfosuccinic acid ester of a C to C fatty acid amide of a hydroxyalkyl primary amine.

3. A process according to claim 1, in which the collector is a sodium salt of the sulfosuccinic acid ester of the oleic acid amide of monoethanolamine or monoisopropanolamine.

4. A process according to claim 1 in which said potassium chloride is seperated from the residue salts resulting from said kainite flotation step by subjecting them to a second froth flotation with a collector in the form of a water-soluble salt of a long chain aliphatic amine.

5. A process according to claim 1 wherein a chemical depressant is added between the flotation operations to depress the effect of the kainite collector during the potassium chloride flotation.

6. A process according to claim 1, wherein the aqueous slurry is a brine containing magnesium chloride and which 5 is essentially saturated with the water-soluble components of the salt mixture.

7. A process according to claim 1, wherein the salt mixture is obtained from the decomposition of a mixture of kainite and carnallite together or with other salts and an aqueous liquor obtained from the decomposition process.

8. A process according to claim 3, in which said p0- tassium chloride is separated from the residue salts resulting from said kainite flotation step by subjecting them to a second froth flotation with a collector in the form of a water-soluble salt of a fatty amine containing from 16 to 22 carbon atms.

6 References Cited UNITED STATES PATENTS 2,173,909 9/ 1939 Kritchevsky 209166 2,236,528 4/1941 Epstein 209166 2,297,664 9/ 1942 Tartaron 209167 FOREIGN PATENTS 1,160,073 2/ 1958 France.

HARRY B. THORNTON,Primary Examiner. ROBERT HALPER, Assistant Examiner. 

